The use of electromagnetic measurements in prior art downhole applications, such as logging while drilling (LWD) and wireline logging applications is well known. Such techniques may be utilized to determine a subterranean formation resistivity, which, along with formation porosity measurements, is often used to indicate the presence of hydrocarbons in the formation. Moreover, azimuthally sensitive directional resistivity measurements are commonly employed e.g., in pay-zone steering applications, to provide information upon which steering decisions may be made.
Methods for employing axial and transverse antennas for acquiring fully gain compensated measurements of the three-dimensional impedance tensor of the formation have been disclosed. While such measurements advantageously contain information on formation resistivity anisotropy, dip, bed boundaries and other aspects of formation geometry, their use may require extensive retooling (i.e., the use of new downhole hardware). Commercial logging tools commonly make use of tilted antennas to obtain directional resistivity measurements. However, such measurements can be susceptible to gain mismatch errors as there are no known methods for providing fully gain compensated propagation measurements using tilted antennas.